Phase I Environmental Site Assessment and Limited Subsurface Investigation


 Identification of recognized environmental conditions allows for better planning and construction design. Researching current and historical uses of a property to identify if those uses have the potential to impact soil or groundwater and could pose a risk to environment or human health also allows developers and property owners to understand potential environmental liability associated with their projects.

Project Characteristics:

Ensolum completed an American Society of Testing and Materials (ASTM) E1527-13 and US Environmental Protection Agency (EPA) “All appropriate Inquiries” compliant Phase I Environmental Site Assessment (ESA) for a land parcel in Navajo Nation Arizona, as part of due diligence to understand the comprehensive history of the Subject Property.  Ensolum worked closely with the client to understand the goal and purpose of the project, while maintaining a balance with the project timeline and budget of the project . The Phase I ESA was completed with the following main four main components as required by ASTM standard E1527-13 and AAI: Records Review, Site Reconnaissance, Interviews, and Summary Report.  An Environmental Professional, as defined in 40 Code of Federal Regulations (CFR) Part 312.10, reviewed and issued the Phase I ESA. 

Findings for the Phase I ESA included the identification of an on-site Recognized Environmental Condition (REC): a historical unpermitted landfill. Additionally, off-site RECs included leaking underground storage tanks (LUST) in close proximity to the Subject Property. 

Photo 1: Construction footprint

   To further investigate the REC, Ensolum completed a Limited Subsurface Investigation (LSI) based on the condition that the buried waste was within the construction footprint of a planned development of a sports complex. The primary objectives of the LSI were to further define the nature and extent of the fill/refuse material and to estimate the volume of material that may need to be disposed of or addressed during construction. A secondary objective was to evaluate the presence or absence of chemicals of concern (COCs) resulting from the presence of the historical landfill and the potential of those COCs to impact subsurface soil and groundwater. The Subject Property is subject to regulatory oversight by the EPA and therefore, COCs were compared to the EPA Residential Regional Screening Levels (RSLs). Soil borings were installed utilizing a hollow stem auger drilling rig with continuous core bit and soil samples were collected based on photo-ionization detection (PID) screening or visual and/or olfactory evidence of impairment. A final report was submitted to the client which included a written summary of findings and recommendations. 

Photo 2: Drill cuttings consisting of landfill material from the subsurface

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